What are the key teaching points for pseudoephedrine?

Peter is seen in the clinic with symptoms of a cold. The health care provider recommends that he take pseudoephedrine. Peter is unfamiliar with pseudoephedrine and the use of the correct dosing.

a) What are the key teaching points for pseudoephedrine?

b) What is the biggest drug–drug interaction problem with over-the-counter cold remedies?